The pressing of glass articles in known in the art and has been described in numerous patent applications such as U.S. Pat. No. 4,362,429 (describing a method and apparatus for pressing glass articles from molten sheet glass), U.S. Pat. No. 4,797,144 (describing a method for pressing and molding optical elements), U.S. Pat. No. 5,122,177 (describing a method for pressing sheet glass to form curved automobile windows), U.S. Pat. No. 5,192,353 (describing a method for pressing near net-shape glass articles), U.S. Pat. No. 5,213,603 (describing a plunger/ring apparatus for press-forming glass articles), and U.S. Pat. No. 5,695,537 (describing a method for bending glass sheet to form a curved glass shape).
Glass pressing processes are typically used to produce glass articles such as TV panels, drinking glasses, dishes, flower vases, ashtrays, and also to form performs that will be blow molded in a subsequent step (the “press and blow” method). In these processes a “gob” of molten glass is placed in a mold and a plunger is pressed onto the glass gob to form the article. However, such methods for forming glass articles are not used with small thin sheets of glass such as are described herein. Additional, such methods are performed at viscosities less than the softening point (107.6 Poise) and frequently create “thin spots” in the glass, which are detrimental to the strength of the final article, due to non-uniform glass thickness of the pressed gob. Articles made at lower viscosities also have greater distortion and are unsuitable for high precision forming.
While the foregoing patents describe the formation of glass articles, they have not been found to be useful in the formation of uniformly thin precision glass articles such as those that can be used as housings in small electronic devices; for example, cell phones, personal music devices, calculators and other small devices. The methods known in the art do not enable the formation of thin glass articles that that can be used in such devices. Consequently, it is highly desirable to develop a process that enables the formation of thin glass articles with dimensional tolerances less than 0.2 mm that can be used in a wide variety of devices.